New compounds for the therapy of chronic viral hepatitis, such
as nucleoside analogs, antisense oligonucleotides or ribozymes,
have been developed in the past several years. Although many are
effective inhibitors of viral replication in vitro, efficacy in
vivo and further clinical applications is often hampered by broad
biodistribution and extraheptic toxicity after systemic
administration. Because the liver is the primary site of infection
and damage in viral hepatitis, specific targeting of antiviral
drugs to hepatocytes may be useful. For this purpose, particle-type
carriers such as liposomes and endogenous lipid particles, as well
as soluble drug carriers, especially ligands of the highly liver-
selective asialoglycoprotein receptor, are currently under
investigation. The use of these compounds could result in the
efficient delivery of various new agents to the liver, and in the
clinical application of new antiviral drugs in the future.